1. Field of the Invention
The present invention relates generally to a means of triggering a controlled combustion within a container, and also a device for transferring heat.
2. Description of the Related Art
A chemical reaction resulting from mixing water or methanol (or other hydrogen-bearing fuel) with sodium borohydride (or other hydride) includes a release of hydrogen gas and heat. Such reaction can be accelerated or moderated by the presence of certain catalysts, including, for example, metals such as nickel, cobalt, Raney nickel, certain pigments, and other materials.
Hydrogen produced from such chemical reaction can be used in the presence of air to purge a surface of a flameless catalytic combustor of hydrogen bearing fuels, for example, fuels such as methanol or ethanol. As such, the hydrogen may aid in a passive self-start of flameless combustion in the presence of such fuels and air of a flameless catalytic combustor.
It is known that an alcohol fueled flameless catalytic heater is most efficient when the fuel, in the form of a vapor, reaches the catalyst at the same time as oxygen reaches the catalyst. This is true of almost all combustion reactions of liquid fuels, as it is the vapor that combusts.
The heat released by an exothermic chemical reaction, an exemplary reaction being mixing sodium borohydride with methanol, will heat the methanol and therein aid in the methanol's vaporization. Vaporization of a fuel such as methanol can be of particular assistance when the fuel is relatively cold, such as in winter seasons or arctic regions. Depending on various factors, the heat released could be sufficient to cause a small amount of fuel actually to boil and thereby produce vaporized fuel quite rapidly.
The heat released by an electric heating element can warm a liquid fuel or a gel fuel. This can be of particular assistance when the fuel is cold, such as in the winter season or arctic regions. Like above, depending on various factors, the heat released could be sufficient to cause a small amount of fuel actually to boil and thereby produce vaporized fuel quite rapidly.
Storage and transportation of alcohol-based fuels is less dangerous when the alcohol-based fuel is transported in the form of a gel. However, since the fuel is a gel, the alcohol's vapor pressure is much lower than when it is in its liquid form. Essentially, this means that the fuel is not as easily used as a fuel in flameless catalytic heaters, as well as other applications, including, for example, direct methanol fuel cells. If, however, the fuel in the form of gel could be re-liquified when desired, there could be advantages in the increased applications in which the alcohol-base fuel could be used.
A gelled alcohol, e.g. in a fuel can, can be combined with sodium borohydride or other similar alkali metal hydride to cause the alcohol-based gel to re-liquefy and the mixture to release hydrogen gas. In addition, heat will be released in such exothermic chemical reaction.
In applications and equipment designs where a liquid form of alcohol-based fuel is preferred, the re-liquefaction of gelled fuel is advantageous both in fuel logistics and for performance. In some applications, such as a flameless catalytic heater, it is possible to thermally attach the heater to a fuel container. In thermally attaching the heater to the fuel container, it may be advantageous to use a thermal conductor from the heater to the fuel in order to heat the fuel to produce a fuel vapor. However, in some applications this may not be practical or possible. In the circumstances in which it is not practical or possible to use a thermal conductor from the heater to the fuel, sodium borohydride or similar chemical can be introduced to re-liquefy and begin heating the fuel. The introduction of the sodium borohydride or similar chemical can be conducted in the fuel storage container or a separate liquefying chamber, thereby enabling the liquefied fuel to flow through tubing and the like to reach the point of its use.
Catalysts such as platinum, palladium, etc. are known to become inert over time. A vapor of methanol fuel which can readily self start its flameless catalytic combustion on a particular catalyst in air may encounter difficulty self starting on the very same catalyst a few months later. The particular causes of catalysts becoming inert are not all known. However, a catalyst that has become inert with time can be “re-activated” by hydrogen self-ignition. The hydrogen for re-activating a catalyst can come from one or more sources, including, for example, a tank or a bladder which releases the hydrogen toward the catalyst prior to or simultaneously with the main fuel. Alternatively, the hydrogen can be chemically or electrolytically produced. Chemical production of hydrogen can be accomplished, for example, via the reaction of sodium borohydride with water, methanol, and/or other hydrogen bearing liquids.
Thus, what is desired is a means for starting a controlled combustion and a means of transferring heat created from controlled combustions.